Which of the molecules in Exercise 110 have net dipole moments (are polar)?

Name: Problem 114, Chapter 8: Chemistry
Uploaded: 2019-08-22T20:05:39-08:00
Duration: 5 min 33 s
Channel: Lena Jake
Description: Which of the molecules in Exercise 110 have net dipole moments (are polar)?

Which of the molecules in Exercise 110 have net dipole...

Key Concepts

Molecular Polarity

Molecular polarity refers to the distribution of electrical charge across a molecule, resulting in a net dipole moment when the centers of positive and negative charges do not coincide. It is determined by both the polarity of individual bonds and the overall molecular geometry.

Electronegativity

Electronegativity is the measure of an atom's ability to attract shared electrons in a bond. Differences in electronegativity between atoms in a bond can lead to polar bonds, which contribute to the overall dipole moment of a molecule.

Vector Addition of Dipole Moments

Since dipole moments are vector quantities, their overall effect in a molecule is determined by the vector sum of the individual bond dipoles. This means that the direction and magnitude of each bond dipole influence whether they cancel out or add up to create a net dipole moment.

Molecular Geometry and Symmetry

The three-dimensional arrangement of atoms in a molecule (its molecular geometry) plays a crucial role in determining polarity. Even when bonds are polar, a symmetric arrangement can lead to a cancellation of individual bond dipoles, resulting in a nonpolar molecule. Conversely, asymmetry can result in a net dipole moment.

Transcript

00:01 So in this video, we're going to talk about question 124 from chapter 8, which asks us which of the molecules in exercise 120 have net dipole moments.

00:11 So in 120, part 8, we were given the molecule pcl3.

00:16 So let's draw the lewis structure for that.

00:18 So we know that our phosphorus atom is going to bring five valence electrons, and each of our chlorine atoms will bring seven valence electrons.

00:25 There's three of them, so that's 21.

00:27 So we have a total of 26 electrons.

00:29 So let's go ahead and draw our central phosphorus atom with three chlorine atoms surrounding it.

00:37 And then if we fill in the octets on our chlorine atoms, that'll use up eight times three electrons.

00:45 So eight times three is 24.

00:46 26 minus 24 tells us we have two electrons left over so i can put the two electrons on my central atom.

00:57 So the general structure i have is ax3e, meaning i have three atoms bonded to my central atom a, and i have one electron pair around that e.

01:13 So when we have an ax3e structure, what we call that is a trigonal pyramidal structure, a trigonal pyramidal structure.

01:23 A trigonal pyramid.

01:29 So what's that going to look like? it's going to look like our lone pair of electrons above the phosphorus atom and our three chlorine atoms below the phosphorus atom.

01:43 So these three chlorine atoms are the points of a tetrahedron, and the fourth point in the tetrahedron is this lone pair of electrons.

01:51 But the fact that we have these lone pair of electrons present pushes the chlorine atoms down out of the plane of the phosphorus atom and gives us a net dipoleum.

02:01 Moment.

02:03 So we do have a net dipole moment in pcl3.

02:07 In b of question 120, we were given as cl2.

02:12 So we know that our sulfur is going to bring six valence electrons and then both of our chlorine atoms will bring seven valence electrons.

02:19 So i have a total of 20 electrons...

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